1. Field of the Invention
The present invention relates to agricultural harvesters, more specifically to systems for controlling the position of headers on harvesters, and still more specifically to ground proximity detection systems for headers operated in both fixed and rigid modes.
2. Description of the Related Art
An agricultural harvester known as a “combine” has been termed such because it combines multiple harvesting functions in a single harvesting unit, such as cutting or picking, threshing, separating and cleaning. A typical combine includes a header that removes the crop from a field, and a feeder housing that transports the crop matter into a threshing and cleaning section where the desirable grain is separated from the undesirable non-grain material. The cleaned grain is transported to an onboard grain storage tank or hopper, and non-grain crop material such as stalks, stems or leaves from the threshing and cleaning section proceeds through a residue system, which may utilize a chopper to process the non-grain material and direct it out the rear of the combine. When the onboard grain storage tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
In many agricultural harvesters the manner in which the header is deployed for use in harvesting a crop can be changed. For example, when harvesting some crops in some field conditions, it is desirable to position the header in a so-called rigid mode, with the header more or less rigid across the width of the machine and at a fixed orientation relative to the ground surface. Under other crop and/or field conditions it can be preferred to use a so-called flex mode header arrangement in which the header more or less floats over the field surface. On wide headers, sections across the width of the header can move somewhat independently relative to other sections, to move up or down, forward or back and/or tilt side to side in response to field surface conditions. Some harvesting heads for agricultural harvesters can be operated selectively in either the so-called rigid mode or in the so-called flex mode.
It is desirable to have ground-sensing systems for both rigid mode and flex mode operation so that the header can be adjusted as necessary when encountering field irregularities, obstacles or obstructions, elevational changes and the like. On headers that can be operated in both the rigid mode and the flex mode, it is known to provide two separate systems for header height control, one for cutting with the header riding on the ground in flex mode and one for cutting with the header operating off the ground in rigid mode. Having separate systems requires separate sensors, wires and some other system components. Changing between flex mode and rigid mode requires switching between the different sensing systems, and requires unplugging sensors for the mode being switched from and plugging into the sensors for the mode being switched to. Switching from one sensor system to the other sensor system also may require recalibrating the combine-header interface. While these tasks are not particularly difficult or burdensome individually, collectively they make the process of switching from one mode to the other mode more time-consuming, and the large number of steps required to switch from one mode to the other mode increase the opportunity for error if unplugging from one sensor or plugging into another sensor is overlooked inadvertently. Further, the act of plugging and unplugging sensors causes wear, thereby increasing the potential for failure.
Accordingly, what is needed in the art is a header height control system that can be operated in both rigid mode and flex mode header operation, without significant adjustment or change when switching from one header operating mode to the other header operating mode.